Pssst! You! Yeah, you... are a passenger on a planet... on a blue-green planet that's orbiting a golden star. And right now we are traveling through a part of our yearly orbit where those of us who live in the northern hemisphere are enjoying longer days and shorter nights than at any other time of year. All this light is what gives us summer. Our longest days are around June 20th to the 22nd - and we call this the summer solstice. But our hottest weather is not until after the solstice (after our days begin shortening) because our rocks, our soil and our bodies of water take time to heat up.

I love this time just before the summer solstice. I can bask in the Sun's light without being distracted by the heat - and the sweat - that are soon to follow. This is when my brain lights up, crackling and sparkling with questions about light. Because light is a mystery to us. Even though you see light all around you (and even though light makes it possible for you to see), nobody knows what light actually is.

If you could hop onto a light ray and ride it, you'd be traveling at the speed of light. At this speed you can circle the Earth 7.5 times every second! Our Sun's light, traveling at this speed, takes 8 minutes to reach us. So we say that the Sun is 8 light minutes away. The light from the reddish star, Antares, that's dominating our southeastern sky these June evenings takes 600 years to reach us. So we're seeing Antares as it was 600 years ago. In fact, we're seeing all of the stars, not as they are, but as they were. Light makes it possible to peer into the past.

Antares is old and dying. (This is why it has the reddish color that we also see in the dying embers at the end of a fire.) Since Antares is dying, and since we're seeing it in the past, it might already be dead. So, when we looking at Antares, we might be seeing something that's not really there. If we can see something that's not really there, what does "really" mean?

OK now, let me ask you to turn on your imagination. Imagine something that disappears whenever it stops moving. This thing cannot be an ordinary object like a car, a person, or a baseball that's been hit into the air! No, this thing that stops existing when it stops moving is more than ordinary. In fact, it is light. Light is not a thing: it's an action. But what is doing the action? Is light doing itself?

Yes, as you and I travel through this de-light-ful part of our orbit that we call June, you might want to enjoy peering 600 years into the past by checking out Antares. Or you might want to do what Albert Einstein did when he discovered what happens at the speed of light; you might want to imagine yourself riding on a light ray. I wonder where your imagination will take you...

This is Harriet Witt, your guide for this little ride on our passenger planet.


If you have any questions, drop Harriet an email: harriet@passengerplanet.com


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